In the air conditioner market, two electronic expansion valves are employed since an indoor unit is disposed far away from an outdoor unit of an air conditioner. In addition, each of the two electronic expansion valves is required to be connected to a respective one-way valve in parallel to improve the system efficiency to the greatest extent. The schematic diagram of the system of the air conditioner is shown in FIG. 1, and the working principle is briefly described as follows.
The refrigerating operation is described as follows. Gaseous refrigerant with high temperature and high pressure which is discharged from a gas discharge pipe of a compressor 7′8 passes through, in turn, a connecting pipe D and a connecting pipe E of a four-way valve 7′1, an outdoor heat exchanger 7′2 (releasing heat by condensation), a first one-way valve 7′4 (here, a first electronic expansion valve 7′3 does not function to regulate the flow), and a second electronic expansion valve 7′5 (here, a second one-way valve 7′6 is closed, and the second electronic expansion valve 7′5 functions to regulate the flow), and finally enters into an indoor heat exchanger 7′7 to be evaporated, so as to absorb heat to realize the refrigerating function. Here, the second electronic expansion valve 7′6 is close to the indoor heat exchanger 7′7, thus the heat loss may be reduced (if the electronic expansion valve is too far away from the evaporator, the liquid refrigerant with low temperature and low pressure which is discharged from the electronic expansion valve is apt to be gasified, which not only causes heat loss, but also results in significant reduction of the utilization rate of the evaporator). Also, if the refrigerant with medium temperature and high pressure which is discharged from the outdoor heat exchanger 7′2 passes through the first electronic expansion valve 7′3, a throttling effect may still occur even when the expansion valve is fully opened, which reduces the pressure of the refrigerant, and then when the refrigerant is transferred to the second electronic expansion valve 7′5, it is apt to be gasified partly, therefore the throttling effect of the electronic expansion valve is adversely affected, and the system efficiency is reduced.
The heating operation is described as follows. Gaseous refrigerant with high temperature and high pressure which is discharged from the gas discharge pipe of the compressor 7′8 passes through, in turn, the connecting pipe D and a connecting pipe C of the four-way valve 7′1, the indoor heat exchanger 7′7 (releasing heat by condensation), the second one-way valve 7′6 (here, the second electronic expansion valve 7′5 does not function to regulate the flow), the first electronic expansion valve 7′3 (here, the first one-way valve 7′4 is closed, and the first electronic expansion valve 7′3 functions to regulate the flow), and finally enters into the outdoor heat exchanger 7′2 to be evaporated, so as to absorb heat to realize the refrigerating function. Here, the first electronic expansion valve 7′3 is close to the outdoor heat exchanger 7′2, thus the heat loss may be reduced (if the electronic expansion valve is too far away from the evaporator, the liquid refrigerant with low temperature and low pressure which is discharged from the electronic expansion valve is apt to be gasified, which not only causes heat loss, but also results in significant reduction of the utilization rate of the evaporator). Also, if the refrigerant with medium temperature and high pressure which is discharged from the indoor heat exchanger 7′7 passes through the second electronic expansion valve 7′5, the throttling effect may still occur even when the expansion valve is fully opened, which reduces the pressure of the refrigerant, and then when the refrigerant flows to the first electronic expansion valve 7′3, it is apt to be gasified partly, therefore the throttling effect of the electronic expansion valve is adversely affected, and the system efficiency is reduced.
However, in the current market, some customers require to integrate the one-way valve with the electronic expansion valve, so as to reduce the numbers of parts and solder joints, and to further improve the reliability of the system.
In view of this, in the conventional technology, an electronic expansion valve with function of a one-way valve is disclosed in Japanese Patent Application Publication No. 2010-249246. Reference may be made to FIGS. 2 and 3. FIG. 2 is a schematic view showing the structure of an electronic expansion valve in the conventional technology which is performing a flow regulation when the refrigerant flows forwards; and FIG. 3 is a schematic view showing the structure of the electronic expansion valve in the conventional technology, wherein the electronic expansion valve is opened when the refrigerant flows reversely.
As shown in FIGS. 2 and 3, a valve core seat 22 is fixed in a valve seat 20, and a valve port 22a is provided in the valve core seat 22. A plurality of small holes 72 are distributed around the valve port 22a. An inlet connecting pipe seat 45 and the valve seat 20 are connected by screw threads to form a main valve body. A secondary valve cavity is formed between the valve seat 20 and the inlet connecting pipe seat 45, and a one-way valve core 60 is provided in the secondary valve cavity. When the refrigerant flows forwards (that is, the refrigerant flows from an inlet connecting pipe 17 to an outlet connecting pipe 16), the inlet connecting pipe 17 is in a high pressure zone and the outlet connecting pipe 16 is in a low pressure zone, thus the one-way valve core 60 is pushed towards the valve core seat 22 to close the small holes 72, and then a valve needle 24 is driven by a drive mechanism to move close to or away from the valve port 22a, thereby regulating an opening of the valve port 22a, and realizing the flow regulation of the system. When the refrigerant flows reversely (that is, the refrigerant flows from the outlet connecting pipe 16 to the inlet connecting pipe 17), the outlet connecting pipe 16 is in the high pressure zone and the inlet connecting pipe 17 is in the low pressure zone, thus the one-way valve core 60 is pushed away from the valve core seat 22 to open the small holes 72, and the refrigerant mostly flows through the small holes 72. Since a plurality of small holes 72 may be provided, a sum of flow areas of the small holes is large, which may greatly reduce the flow resistance of the product.
However, the conventional electronic expansion valve described above has the following defects.
Firstly, in the above structure, the one-way valve core 60 is provided at a lower portion of the valve core seat 22, and the one-way valve core 60 and the valve needle 24 are respectively arranged at two sides of the valve core seat 22. When the refrigerant flows forwards, the refrigerant may generate a large upward impact force, which requires that a buffer spring provided in the valve needle 24 has a large spring force to ensure the sealing performance of the valve needle 24 under a high pressure condition. However, a series of problems may be caused when the spring force is increased, for example, the difficulty of rotation of the valve needle 24 may be increased, and the size of the product may be increased. Generally, it is fairly well that the spring can be designed to ensure the sealing performance when subjected to a refrigerant pressure of 2.5 Mpa, and the product of this structure is hard to ensure the sealing performance under a refrigerant pressure of 3.5 MPa.
Secondly, the one-way valve 60 is mounted at the lower portion of the valve core seat 22, which further requires the one-way valve 60 to have a certain stroke, thus it inevitably requires the lower portion of the valve core seat 22 to have a large mounting space, which may increase the axial height of the valve body.
Thirdly, the one-way valve core 60 is required to be provided with a bypass flow passage 70, thus when flowing reversely, the refrigerant needs to pass through the bypass flow passage 70, which results in a large reverse flow resistance. On this basis, in order to reduce the reverse flow resistance, the valve seat 20 is required to have a sufficiently large diameter, which may in turn result in a large radial dimension of the valve seat 20.